The Diet Trick That Will Keep Jet Lag at Bay This Thanksgiving

If you want to cross time zones happily, forget about sidling up to the terminal sushi bar or accepting the cute in-flight peanut bags. Scientists suspect that fasting for 16 hours before your plane touches down can reset your body clock better than any ritual to do with arnica, Ambien, or Evian.

Jet lag can manifest as a headache, grumpiness, decreased alertness, and the inability to sleep—or, more likely, it manifests as all of the above. The condition is the result of misalignment between the external environment and internal body clock, a cluster of 20,000 neurons located in our brain near our optic nerves. Our master body clock is busy coordinating body functions including temperature, blood pressure, and hormone production over a 24-hour cycle, and can withstand about one hour’s displacement a day.

The most influential cue on the body clock is light, yet scientists have discovered that a second master clock in the brain responds to the time we eat (and don’t eat). A brief bout of self-deprivation effectively puts the clock on hold, and it comes back to life with the reintroduction of food. Scientists believe our bodies suspend their biological clocks when we are hungry as a leftover from the prehistoric ages when hungry people needed to stay awake in order to forage. Their body clocks returned to regular programming once they had obtained the food they needed.

Abstaining from food and then indulging in a big meal at the moment we want our body to believe it’s morning is a hack that has been used by everybody from jet-setting race car drivers to Ronald Reagan.

The first scientist to come out with this jet-lag strategy, chronobiologist Charles Ehret, suggested that a traveler alternate days of fasting with days of very light eating (a high protein lunch, and carb-based dinner) a full week before her flight. She could then eat a little bit in the air, and indulge in a big breakfast at 7:30 a.m. in her new time zone. A streamlined version comes to us courtesy of a research team from Harvard and Beth Israel Deaconess Medical Center in Boston that located the second biological clock. “This all came out of a paper we published on how the brains of mice readjusted when they were only fed once a day,” says Clifford B. Saper, M.D., Ph.D., head of Beth Israel’s department of neurology. “I simply made a conjecture that fasting and then eating again probably works as a way to reset the biological clock on humans as well.” Saper has yet to run a clinical trial on humans, yet he has found fasting for 16 hours before deplaning to be a successful way to prevent jet lag when he travels, and he has received a dozen letters from people who have found the technique to be successful.

A word of caution to those who wish to try out the fast: A traveler must stay hydrated—“Water doesn’t cause the clock to readjust, calories do,” explains Saper. Just pray for really good in-flight movies, and think about all the treats that you are duty-bound to devour once you clear customs.